考虑气温变化影响的引水渠道水内冰演变数值模拟

Numerical Simulation of Frazil Ice Evolution in Diversion Channel Considering Effect of Temperature Variation

高寒地区冰害问题是关系到引水式水电站能否正常运行的关键问题.为此,建立了三维非稳态Euler-Euler两相流k-ε紊流模型,在动量方程中考虑了相间曳力、升力、虚拟质量力,在热量传递方程中考虑了冰水之间的热量传递以及太阳辐射、有效辐射、蒸发热损失和水面对流热损失等.以新疆某水电站引水渠道为例,模拟分析了气温变化条件下流速、水温、冰温及冰体积分数的沿程分布.结果表明:水温沿程先降低后增大,沿程出现最低点,冰温沿程逐渐增大;冰体积分数沿程存在突变点,且突变点在水温最低点附近;随着气温降低,最终的产冰量和冰体积分数逐渐增大.讨论了太阳辐射、有效辐射和蒸发热损失对水内冰分布的影响,并通过与吴剑疆等的黄河上游河道中水内冰演变计算结果及经验公式计算产冰量的对比分析,验证了模型的可靠性.

Ice damage is the key problem hindering normal operation of hydropower stations especially the diversion hydropower stations in high altitude and cold regions. A 3-D unsteady Euler-Euler two-phase k-ε turbulence model has been developed, in which the drag, virtual mass and lift force are considered in the momentum transfer term and thermal transfer between ice and water, solar radiation, effective radiation, evaporative heat loss and convective heat loss on water surface are considered in the thermal transfer term. Water velocity, water temperature, ice temperature and ice volume fraction along the channel under various air temperature conditions have been simulated and analyzed with the diversion channel of a hydropower station in Xinjiang as a case. Analysis results show that ice temperature increases gradually along the channel while water temperature first drops and then rises along the channel with a low- est value. A sudden point of ice volume fraction has been identified along the diversion channel, which is close to the spot with the lowest water temperature. With the decrease of air temperature, both ice quantity and ice volume fraction increase gradually. The effect of solar radiation, effective radiation and evaporative heat loss on distribution of frazil ice has been discussed, and the comparison with the frazil ice evolution results in the upper Yellow River reported by Wu Jianjiang et al and the empirical ice quantity has verified reliability of the model.